FILTERING, CONTROL AND FAULT DETECTION WITH RANDOMLY OCCURRING INCOMPLETE INFORMATION

Transcription

1 FILTERING, CONTROL AND FAULT DETECTION WITH RANDOMLY OCCURRING INCOMPLETE INFORMATION

2 FILTERING, CONTROL AND FAULT DETECTION WITH RANDOMLY OCCURRING INCOMPLETE INFORMATION Hongli Dong Northeast Petroleum University, China Zidong Wang Brunel University, UK Huijun Gao Harbin Institute of Technology, China

3 This edition first published 2013 C 2013 John Wiley & Sons, Ltd Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For detailsof our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Dong, Hongli, 1977 Filtering, control and fault detection with randomly occurring incomplete information / Hongli Dong, Zidong Wang, Huijun Gao. pages cm Includes bibliographical references and index. ISBN (cloth) 1. Automatic control. 2. Electric filters, Digital. 3. Fault tolerance (Engineering) I. Wang, Zidong, 1966 II. Gao, Huijun. III. Title. TJ213.D dc A catalogue record for this book is available from the British Library ISBN Typeset in 10/12pt Times by Aptara Inc., New Delhi, India

4 The time is boring without random occurrence The research is monotonous without incomplete information The life is tedious without fault detection The living is tough without noise filtering The power is nothing without control This book is dedicated to the Dream Dynasty, consisting of a group of simple yet happy people who are falling in love with both the random incompleteness and the incomplete randomness by detecting the faults, filtering the noises, and controlling the powers...

5 Contents Preface Acknowledgments List of Abbreviations List of Notations xi xiii xv xvii 1 Introduction Background, Motivations, and Research Problems Randomly Occurring Incomplete Information The Analysis and Synthesis of Nonlinear Stochastic Systems Distributed Filtering over Sensor Networks Outline 7 2 Variance-Constrained Finite-Horizon Filtering and Control with Saturations Problem Formulation for Finite-Horizon Filter Design Analysis of H and Covariance Performances H Performance Variance Analysis Robust Finite-Horizon Filter Design Robust H Finite-Horizon Control with Sensor and Actuator Saturations Problem Formulation Main Results Illustrative Examples Example Example Summary 36 3 Filtering and Control with Stochastic Delays and Missing Measurements Problem Formulation for Robust Filter Design Robust H Filtering Performance Analysis Robust H Filter Design 50

6 viii Contents 3.4 Robust H Fuzzy Control Problem Formulation Performance Analysis Controller Design Illustrative Examples Example Example Example Summary 72 4 Filtering and Control for Systems with Repeated Scalar Nonlinearities Problem Formulation for Filter Design The Physical Plant The Communication Link The Filter The Filtering Error Dynamics Filtering Performance Analysis Filter Design Observer-Based H Control with Multiple Packet Losses Problem Formulation Main Results Illustrative Examples Example Example Example Example Summary 99 5 Filtering and Fault Detection for Markov Systems with Varying Nonlinearities Problem Formulation for Robust H Filter Design Performance Analysis of Robust H Filter Design of Robust H Filters Fault Detection with Sensor Saturations and Randomly Varying Nonlinearities Problem Formulation Main Results Illustrative Examples Example Example Example Example Summary Quantized Fault Detection with Mixed Time-Delays and Packet Dropouts Problem Formulation for Fault Detection Filter Design Main Results 143

7 Contents ix 6.3 Fuzzy-Model-Based Robust Fault Detection Problem Formulation Main Results Illustrative Examples Example Example Summary Distributed Filtering over Sensor Networks with Saturations Problem Formulation Main Results An Illustrative Example Summary Distributed Filtering with Quantization Errors: The Finite-Horizon Case Problem Formulation Main Results An Illustrative Example Summary Distributed Filtering for Markov Jump Nonlinear Time-Delay Systems Problem Formulation Deficient Statistics of Markovian Modes Transitions The Network Topology Descriptions of the Target Plant and the Sensor Network Main Results An Illustrative Example Summary A New Finite-Horizon H Filtering Approach to Mobile Robot Localization Mobile Robot Kinematics and Absolute Measurement Kinematic Model Measurement Model with Quantization and Missing Observations A Stochastic H Filter Design Simulation Results Summary Conclusions and Future Work Conclusions Contributions Future Work 250 References 253 Index 261

8 Preface In the context of systems and control, incomplete information refers to a dynamical system in which knowledge about the system states is limited due to the difficulties in modeling complexity in a quantitative way. The well-known types of incomplete information include parameter uncertainties and norm-bounded nonlinearities. Recently, in response to the development of network technologies, the phenomenon of randomly occurring incomplete information has become more and more prevalent. Such a phenomenon typically appears in a networked environment. Examples include, but are not limited to, randomly varying nonlinearities (RVNs), randomly occurring mixed time-delays (ROMDs), randomly occurring multiple time-varying communication delays (ROMTCDs), and randomly occurring quantization errors (ROQEs). Randomly occurring incomplete information, if not properly handled, would seriously deteriorate the performance of a control system. In this book, we investigate the filtering, control, and fault detection problems for several classes of nonlinear systems with randomly occurring incomplete information. Some new concepts are proposed which include RVNs, ROMDs, ROMTCDs, and ROQEs. The incomplete information under consideration mainly includes missing measurements, time delays, sensor and actuator saturations, quantization effects, and time-varying nonlinearities. The content of this book can be divided into three parts. In the first part, we focus on the filtering, control, and fault detection problems for several classes of nonlinear stochastic discrete-time systems with missing measurements, sensor and actuator saturations, RVNs, ROMDs, and ROQEs. Some sufficient conditions are derived for the existence of the desired filters, controllers, and fault detection filters by developing new techniques for the considered nonlinear stochastic systems. In the second part, the theories and techniques developed in the previous part are extended to deal with distributed filtering issues over sensor networks, and some distributed filters are designed for nonlinear time-varying systems and Markovian jump nonlinear time-delay systems. Finally, we apply a new stochastic H filtering approach to study the mobile robot localization problem, which shows the promising application potential of our main results. The book is organized as follows. Chapter 1 introduces some recent advances on the analysis and synthesis problems with randomly occurring incomplete information. The developments of the filtering, control, and fault detection problems are systematically reviewed, and the research problems to be addressed in each individual chapter are also outlined. Chapter 2 is concerned with the finite-horizon filtering and control problems for nonlinear time-varying stochastic systems where sensor and actuator saturations, variance-constrained and missing measurements are considered. In Chapters 3 and 4, the H filtering and control problems are addressed for several classes of nonlinear discrete systems where ROMTCDs and multiple

9 xii Preface packet dropouts are taken into account. Chapter 5 investigates the robust H filtering and fault detection problems for nonlinear Markovian jump systems with sensor saturation and RVNs. In Chapter 6, the fault detection problem is considered for two classes of discrete-time systems with randomly occurring nonlinearities, ROMDs, successive packet dropouts and measurement quantizations. Chapters 7, 8, and 9 discuss the distributed H filtering problem over sensor networks. In Chapter 10, a new stochastic H filtering approach is proposed to deal with the localization problem of the mobile robots modeled by a class of discrete nonlinear time-varying systems subject to missing measurements and quantization effects. Chapter 11 summarizes the results of the book and discusses some future work to be investigated further. This book is a research monograph whose intended audience is graduate and postgraduate students and researchers.

10 Acknowledgments We would like to express our deep appreciation to those who have been directly involved in various aspects of the research leading to this book. Special thanks go to Professor Daniel W. C. Ho from City University of Hong Kong, Professor James Lam from the University of Hong Kong, Professor Xiaohui Liu from Brunel University in the UK, Professor Steven X. Ding from the University of Duisburg Essen in Germany, and Professor Ligang Wu from Harbin Institute of Technology of China for their valuable suggestions, constructive comments, and support. We also extend our thanks to the many colleagues who have offered support and encouragement throughout this research effort. In particular, we would like to acknowledge the contributions from Bo Shen, Liang Hu, Jun Hu, Yurong Liu, Jinling Liang, Guoliang Wei, Xiao He, Lifeng Ma, Derui Ding, Yao Wang, Xiu Kan, Sunjie Zhang, and Nianyin Zeng. Finally, we are especially grateful to our families for their encouragement and never-ending support when it was most required. The writing of this book was supported in part by the National 973 Project under Grant 2009CB320600, the National Natural Science Foundation of China under Grants , , , and , the Engineering and Physical Sciences Research Council (EPSRC) of the UK, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany. The support of these organizations is gratefully acknowledged.

11 List of Abbreviations CCL DFD DKF FHFD HCMDL HFDL HinfFC HinfF LMI MJS NCS OFDFD RFD RHFD RLMI RMM ROMD ROMTCD ROPD ROQE ROSS RVN RDE SAS SPD TP T S cone complementarity linearization distributed filter design distributed Kalman filtering finite-horizon H filter design H control with multiple data losses H filtering with data loss H fuzzy control H filtering linear matrix inequality Markovian jump system networked control system optimized fault detection filter design robust filter design robust H filter design recursive linear matrix inequality randomly missing measurement randomly occurring mixed time-delay randomly occurring multiple time-varying communication delay randomly occurring packet dropout randomly occurring quantization error randomly occurring sensor saturation randomly varying nonlinearity Riccati difference equation sensor and actuator saturation successive packet dropout transition probability Takagi Sugeno

12 List of Notations the n-dimensional Euclidean space the set of all n m real matrices the set of all nonnegative real numbers the set of all nonnegative integers the set of all negative integers OL the class of all continuous nondecreasing convex functions φ : R + R + such that φ(0) = 0 and φ(r) > 0forr > 0 A the norm of matrix A defined by A = tr(a T A) A T the transpose of the matrix A A R n m the Moore Penrose pseudo inverse of A R m n I the identity matrix of compatible dimension 0 the zero matrix of compatible dimension Prob( ) the occurrence probability of the event E{x} the expectation of the stochastic variable x E{x y} the expectation of the stochastic variable x conditional on y (,F, Prob) the complete probability space λ min (A) the smallest eigenvalue of a square matrix A λ max (A) the largest eigenvalue of a square matrix A the ellipsis for terms induced by symmetry, in symmetric block matrices diag{ } the block-diagonal matrix l 2 [0, ) the space of square summable sequences 2 the usual l 2 norm tr(a) the trace of a matrix A min tr(a) the minimization of tr(a) Var {x i } the variance of x i the Kronecker product 1 n 1 n = [1, 1,...,1] T R n e i e i = [0,...,0, 1, 0,...,0] }{{}}{{} X > Y i 1 n i the X Y is positive definite, where X and Y are real symmetric matrices R n R n m R + I + Z X Y the X Y is positive semi-definite, where X and Y are real symmetric matrices

13 1 Introduction In the past decade, networked control systems (NCSs) have attracted much attention owing to their successful applications in a wide range of areas for the advantage of decreasing the hardwiring, the installation cost, and implementation difficulties. Nevertheless, network-related challenging problems inevitably arise due to the physical equipment constraints, the complexity, and uncertainty of the external environment in the process of modeling or information transmission, which would drastically degrade the system performance. Such network-induced problems include, but are not limited to, missing measurements, communication delays, sensor and actuator saturations, signal quantization, and randomly varying nonlinearities. These phenomena may occur in a probabilistic way that is customarily referred to as randomly occurring incomplete information. For several decades, nonlinear analysis and stochastic analysis have arguably been two of the most active research areas in systems and control. This is simply because (1) nonlinear control problems are of interest to engineers, physicists, and mathematicians as most physical systems are inherently nonlinear in nature, and (2) stochastic modeling has come to play an important role in many branches of science and industry as many real-world system and natural processes may be subject to stochastic disturbances. There has been a rich literature on the general nonlinear stochastic control problems. A great number of techniques have been developed on filtering, control, and fault detection problems for nonlinear stochastic systems in order to meet the needs of practical engineering. Recently, with the development of NCSs, the analysis and synthesis problems for nonlinear stochastic systems with the aforementioned network-induced phenomena have become interesting and imperative, yet challenging, topics. Therefore, the aim of this book is to deal with the filtering, control, and fault detection problems for nonlinear stochastic systems with randomly occurring incomplete information. The focus of this chapter is to provide a timely review on the recent advances of the analysis and synthesis issues for complex systems with randomly occurring incomplete information. Most commonly used methods for modeling randomly occurring incomplete information are summarized. Based on the models established, various filtering, control, and fault detection problems with randomly occurring incomplete information are discussed in great detail. Subsequently, some challenging issues for future research are pointed out. Finally, we give the outline of this book. Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information, First Edition. Hongli Dong, Zidong Wang, and Huijun Gao John Wiley & Sons, Ltd. Published 2013 by John Wiley & Sons, Ltd.

14 2 Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information 1.1 Background, Motivations, and Research Problems Randomly Occurring Incomplete Information Accompanied by the rapid development of communication and computer technology, NCSs have become more and more popular for their successful applications in modern complicated industry processes, e.g., aircraft and space shuttle, nuclear power stations, high-performance automobiles, etc. However, the insertion of network makes the analysis and synthesis problems much more complex due to the randomly occurring incomplete information that is mainly caused by the limited bandwidth of the digital communication channel. The randomly occurring incomplete information under consideration mainly includes randomly missing measurements (RMMs), randomly occurring communication delays, sensor and actuator saturations (SASs), randomly occurring quantization and randomly varying nonlinearities (RVNs). Missing Measurements In practical systems within a networked environment, measurement signals are usually subject to missing probabilistic information (data dropouts or packet losses). This may be caused for a variety of reasons, such as the high maneuverability of the tracked target, a fault in the measurement, intermittent sensor failures, network congestion, accidental loss of some collected data, or some of the data may be jammed or coming from a very noisy environment, and so on. Such a missing measurement phenomenon that typically occurs in NCSs has attracted considerable attention during the past few years; see Refs [1 24] and the references cited therein. Various approaches have been presented in the literature to model the packet dropout phenomenon. For example, the data packet dropout phenomenon has been described as a binary switching sequence that is specified by a conditional probability distribution taking on values of 0 or 1 [25, 26]. A discrete-time linear system with Markovian jumping parameters was employed by Shu et al. [27] and Xiong and Lam [28] to construct the random packet dropout model. A model that comprises former measurement information of the process output was introduced by Sahebsara et al. [29] to account for the successive packet dropout phenomenon. A model of multiple missing measurements was proposed by Wei et al. [18] using a diagonal matrix to describe the different missing probability for individual sensors. Communication Delays Owing to the fact that time delays commonly reside in practical systems and constitute a main source for system performance degradation or even instability, the past decade has witnessed significant progress on analysis and synthesis for systems with various types of delays, and a large amount of literature has appeared on the general topic of time-delay systems. For example, the stability of NCSs under a network-induced delay was studied by Zhao et al. [30] using a hybrid system technique. The optimal stochastic control method was proposed by Nilsson [31] to control the communication delays in NCSs. A networked controller was designed in the frequency domain using robust control theory by Gokas [32] in which the network delays were considered as an uncertainty. However, most of the relevant literature mentioned above has focused on the constant time-delays. Delays resulting from network transmissions are inherently random and time varying [33 41]. This is particularly true when signals are transmitted over the internet and, therefore, existing control methods for constant time-delay

15 Introduction 3 cannot be utilized directly [42]. Recently, some researchers have started to model the networkinduced time delays in multi-form probabilistic ways and, accordingly, some initial results have been reported. For example, the random communication delays have been modeled as Markov chains and the resulting closed-loop systems have been represented as Markovian jump linear systems with two jumping parameters [43, 44]. Two kinds of random delays, which happen in the channels from the controller to the plant and from the sensor to the controller, were simultaneously considered by Yang et al. [45]. The random delays were modeled by Yang et al. [45] as a linear function of the stochastic variable satisfying a Bernoulli random binary distribution. Different from Yang et al. [45], the problem of stability analysis and stabilization control design was studied by Yue et al. [46] for Takagi Sugeno (T S) fuzzy systems with probabilistic interval delay, and the Bernoulli distributed sequence was utilized to describe the probability distribution of the time-varying delay taking values in an interval. It should be mentioned that, among others, the binary representation of the random delays has been fairly popular because of its practicality and simplicity in describing communication delays. However, most research attention has been centered on the single random delay having a fixed value if it occurs. This would lead to conservative results or even degradation of the system performance since, at a certain time, the NCSs could give rise to multiple time-varying delays but with different occurrence probabilities. Therefore, a more advanced methodology is needed to handle time-varying network-induced time delays in a closed-loop control system. Signal Quantization As is well known, quantization always exists in computer-based control systems employing finite-precision arithmetic. Moreover, the performance of NCSs will be inevitably subject to the effect of quantization error owing to the limited network bandwidth caused possibly by strong signal attenuation and perturbation in the operational environment. Hence, the quantization problem of NCSs has long been studied and many important results have been reported; see Refs [47 64] and references cited therein. For example, in Brockett and Liberzon [65], the time-varying quantization strategy was first proposed where the number of quantization levels is fixed and finite while at the same time the quantization resolution can be manipulated over time. The problem of input-to-state stable with respect to the quantization error for nonlinear continuous-time systems has been studied by Liberzon [66]. In this framework, the effect of quantization is treated as an additional disturbance whose effect is overcome by a Lyapunov redesign of the control law. A switching control strategy with dwell time was proposed by Ishii and Francis [67] to use as a quantizer for single-input systems. The quantizer employed in this framework is in fact an extension of the static logarithmic quantizer in [68] to the continuous case. So far, there have been mainly two different types of quantized communication models adopted in the literature: uniform quantization [62 64] and logarithmic quantization [56 59, 61]. It has been proved that, compared with a uniform quantizer, logarithmic quantization is more preferable since fewer bits need to be communicated. A sector bound scheme to handle the logarithmic quantization effects in feedback control systems was proposed by Fu and Xie [69], and such an elegant scheme was then extensively employed later on; for example, see Refs [58, 70, 71] and references cited therein. However, we note that the methods in most of the references cited above could not be directly applied to NCSs, because in NCSs the effects of network-included delay and packet dropout should also be considered.

16 4 Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information Sensor and Actuator Saturations In practical control systems, sensors and actuators cannot provide unlimited amplitude signal due primarily to the physical, safety, or technological constraints. In fact, actuator/sensor saturation is probably the most common nonlinearity encountered in practical control systems, which can degrade the system performance or even cause instability if such a nonlinearity is ignored in the controller/filter design. Because of their theoretical significance and practical importance, considerable attention has been focused on the filtering and control problems for systems with actuator saturation [72 82]. As for sensor saturation, the associated results have been relatively few due probably to the technical difficulty [83 88]. Nevertheless, in the scattered literature regarding sensor saturation, it has been implicitly assumed that the occurrence of sensor saturations is deterministic; that is, the sensor always undergoes saturation. Such an assumption, however, does have its limitations, especially in a sensor network. The sensor saturations may occur in a probabilistic way and are randomly changeable in terms of their types and/or levels due to the random occurrence of networked-induced phenomena such as random sensor failures, sensor aging, or sudden environment changes. To reflect the reality in networked sensors, it would make practical sense to consider the randomly occurring sensor saturations (ROSSs) where the occurrence probability can be estimated via statistical tests. Also, it should be mentioned that very few results have dealt with the systems with simultaneous presence of actuator and sensor saturations [89], although such a presence is quite typical in engineering practice. Randomly Varying Nonlinearities It is well known that nonlinearities exist universally in practice, and it is quite common to describe them as additive nonlinear disturbances that are caused by environmental circumstances. In a networked system such as the internet-based three-tank system for leakage fault diagnosis, such nonlinear disturbances may occur in a probabilistic way due to the random occurrence of a networked-induced phenomenon. For example, in a particular moment, the transmission channel for a large amount of packets may encounter severe network-induced congestions due to the bandwidth limitations, and the resulting phenomenon could be reflected by certain randomly occurring nonlinearities where the occurrence probability can be estimated via statistical tests. As discussed in Refs [90 93], in the NCSs that are prevalent nowadays, the nonlinear disturbances themselves may experience random abrupt changes due to random changes and failures arising from networked-induced phenomena, which give rise to the socalled RVNs. In other words, the type and intensity of the so-called RVNs could be changeable in a probabilistic way The Analysis and Synthesis of Nonlinear Stochastic Systems For several decades now, stochastic systems have received considerable research attention in which stochastic differential equations are the most useful stochastic models with broad applications in aircraft, chemical, or process control systems and distributed networks. Generally speaking, stochastic systems can be categorized into two types, namely internal stochastic systems and external stochastic systems [94].

17 Introduction 5 As a class of internal stochastic systems with finite operation modes, Markovian jump systems (MJSs) have received particular research interest in the past two decades because of their practical applications in a variety of areas, such as power systems, control systems of a solar thermal central receiver, NCSs, manufacturing systems, and financial markets. So far, the existing results for MJSs have covered a wide range of research problems, including those for stability analysis [95 97], filter design [98 104], and controller design [105, 106]. Nevertheless, compared with the fruitful results for MJSs for filtering and control problems, MJS use for the corresponding fault detection problem has received much less attention [107, 108], due primarily to the difficulty in accommodating the multiple fault detection performances. In the literature concerning MJSs, most results have been reported by supposing that the transition probabilities (TPs) in the jumping process are completely accessible. However, this is not always true for many practical systems. For example, in NCSs, it would be extremely difficult to obtain precisely all the TPs via time-consuming yet expensive statistical tests. In other words, some of TPs are very likely to be incomplete (i.e., uncertain or even unknown). So far, some initial efforts have been made to address the incomplete probability issue for MJSs. For example, the problems of uncertain TPs and partially unknown TPs have been addressed by Xiong and coworkers [95, 98] and Zhang and coworkers [100, 109], respectively. Furthermore, the concept of deficient statistics for modes transitions has been put forward [110] to reflect different levels of the limitations in acquiring accurate TPs. Unfortunately, the filtering/control/fault detection problem for discrete-time MJSs with RVNs has yet to be fully investigated. For external stochastic systems, stochasticity is always caused by an external stochastic noise signal, and can be modeled by stochastic differential equations with stochastic processes [94, 111]. Furthermore, recognizing that nonlinearities exist universally in practice and both nonlinearity and stochasticity are commonly encountered in engineering practice, the robust H filtering, H control, and fault detection problems for nonlinear stochastic systems have stirred a great deal of research interest. For the fault detection problems, we refer the readers to [82, ] and references cited therein. With respect to the H control and filtering problems, we mention the following representative work. The stochastic H filtering problem for time-delay systems subject to sensor nonlinearities has been dealt with by Wang and coworkers [115, 116]. The robust stability and controller design problems for NCSs with uncertain parameters have been studied by Zhang et al. [44] and Jiang and Han [117], respectively. The stability issue was addressed by Wang et al. [118] for a class of T S fuzzy dynamical systems with time delays and uncertain parameters. In Zhang et al. [119], the robust H filtering problem for affine nonlinear stochastic systems with state and external disturbance-dependent noise was studied, where the filter can be designed by solving second-order nonlinear Hamilton Jacobi inequalities. So far, in comparison with the fruitful literature available for continuous-time systems, the corresponding H filtering results for discrete-time systems has been relatively sparse. Also, to the best of our knowledge, the analysis and design problems for nonlinear discrete-time stochastic systems with randomly occurring incomplete information have not been properly investigated yet, and constitutes the main motivation for this book Distributed Filtering over Sensor Networks In the past decade, sensor networks have attracted increasing attention from many researchers in different disciplines owing to the extensive applications of sensor networks in many areas,

18 6 Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information including in surveillance, environment monitoring, information collection, industrial automation, and wireless networks [ ]. A sensor network typically consists of a large number of sensor nodes and also a few control nodes, all of which are distributed over a spatial region. The distributed filtering or estimation, as an important issue for sensor networks, has been an area of active research for many years. Different from the traditional filtering for a single sensor [111, 103, 128, 129], the information available for the filter algorithm on an individual node of a sensor network is not only from its own measurement, but also from its neighboring sensors measurements according to the given topology. As such, the objective of filtering based on a sensor network can be achieved in a distributed yet collaborative way. It is noted that one of the main challenges for distributed filtering lies in how to handle the complicated coupling issues between one sensor and its neighboring sensors. In recent years, the distributed filtering problem for sensor networks has received considerable research interest and a lot of research results have been available in the literature; for example, see Refs [ , 126, ]. The distributed diffusion filtering strategy was established by Cattivelli and Sayed [140, 122] for the design of distributed Kalman filters and smoothers, where the information is diffused across the network through a sequence of Kalman iterations and data aggregation. A distributed Kalman filtering (DKF) algorithm was introduced by Olfati-Saber and Shamma [142], through which a crucial part of the solution is used to estimate the average of n signals in a distributed way. Furthermore, three novel DKF algorithms were introduced by Olfati-Saber [141], with the first one being a modification of the previous DKF algorithm [142]. Olfati-Saber also rigorously derived and analyzed a continuous-time DKF algorithm [141] and the corresponding extension to the discrete-time setting [124], which included an optimality and stability analysis. It should be pointed out that, so far, most reported distributed filter algorithms for sensor networks have been mainly based on the traditional Kalman filtering theory that requires exact information about the plant model. In the presence of unavoidable parameter drifts and external disturbances, a desired distributed filtering scheme should be made as robust as possible. However, the robust performance of the available distributed filters has not yet been thoroughly studied, and this would inevitably restrict the application potential in practical engineering. Therefore, it is of great significance to introduce the H performance requirement with the hope to enhance the disturbance rejection attenuation level of designed distributed filters. Note that some initial efforts have been made to address the robustness issue. Very recently, a new distributed H -consensus performance was proposed by Shen et al. [143] to quantify the consensus degree over a finite-horizon and the distributed filtering problem has been addressed for a class of linear time-varying systems in the sensor network, and the filter parameters were designed recursively by resorting to the difference linear matrix inequalities (LMIs). Ugrinovskii [144] included an H -type performance measure of disagreement between adjacent nodes of the network and a robust filtering approach was proposed to design the distributed filters for uncertain plants. On the other hand, since nonlinearities are ubiquitous in practice, it is necessary to consider the distributed filtering problem for target plants described by nonlinear systems. Unfortunately, up to now, the distributed nonlinear H filtering problem for sensor networks has gained very little research attention despite its practical importance, and it remains as a challenging research topic.

19 Introduction 7 Figure 1.1 Organizational structure of the book (see List of Abbreviations for the meanings of the abbreviations) 1.2 Outline The organization of this book is shown in Figure 1.1 and the outline of the book is as follows: 1. Chapter 1 has introduced the research background, motivations, and research problems (mainly involving incomplete information, nonlinear stochastic systems, and sensor networks), and concludes by presenting the outline of the book. 2. Chapter 2 addresses the robust H finite-horizon filtering and output feedback control problems for a class of uncertain discrete stochastic nonlinear time-varying systems with

20 8 Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information sensor and actuator saturations, error variance constraints, and multiple missing measurements. In the system under investigation, all the system parameters are allowed to be time varying, and the stochastic nonlinearities are described by statistical means which can cover several classes of well-studied nonlinearities. First, we develop a new robust H filtering technique for the nonlinear discrete time-varying stochastic systems with normbounded uncertainties, multiple missing measurements, and error variance constraints. Sufficient conditions are derived for a finite-horizon filter to satisfy both the estimation error variance constraints and the prescribed H performance requirement. Such a technique relies on the forward solution to a set of recursive linear matrix inequalities (RLMIs) and, therefore, is suitable for online computation. Second, the corresponding robust H finite-horizon output feedback control problem is investigated for nonlinear system with both sensor and actuator saturations. An RLMI approach is employed to design the desired output feedback controller achieving the prescribed H disturbance rejection level. 3. In Chapter 3, the robust H filtering and control problems are studied for two classes of uncertain nonlinear systems with both multiple stochastic time-varying communication delays and multiple packet dropouts. A sequence of random variables, all of which are mutually independent but obey a Bernoulli distribution, are first introduced to account for the randomly occurring communication delays. The packet dropout phenomenon occurs in a random way and the occurrence probability for each sensor is governed by an individual random variable satisfying a certain probabilistic distribution on the interval [0, 1]. First, the robust H filtering problem is investigated for the discrete-time system with parameter uncertainties, state-dependent stochastic disturbances, and sector-bounded nonlinearities. Intensive stochastic analysis is carried out to obtain sufficient conditions for ensuring the exponential stability, as well as prescribed H performance. Furthermore, the phenomena of multiple probabilistic delays and multiple missing measurements are extended, in a parallel way, to fuzzy systems, and a set of parallel results is derived. 4. In Chapter 4, the H filtering and control problems are investigated for systems with repeated scalar nonlinearities and missing measurements. The nonlinear system is described by a discrete-time state equation involving a repeated scalar nonlinearity which typically appears in recurrent neural networks. The communication links, existing between the plant and filter, are assumed to be imperfect and a stochastic variable satisfying the Bernoulli random binary distribution is utilized to model the phenomenon of the missing measurements. The stable full- and reduced-order filters are designed such that the filtering process is stochastically stable and the filtering error satisfies the H performance constraint. Moreover, the multiple missing measurements are included to model the randomly intermittent behaviors of the individual sensors, where the missing probability for each sensor/actuator is governed by a random variable satisfying a certain probabilistic distribution on the interval [0, 1]. By employing the cone complementarity linearization procedure, the observer-based H control problem is also studied for systems with repeated scalar nonlinearities and multiple packet losses, and a set of parallel results is derived. 5. Chapter 5 addresses the filtering and fault detection problems for discrete-time MJSs with incomplete knowledge of TPs, RVNs, and sensor saturations. The issue of RVNs is first addressed to reflect the limited capacity of the communication networks resulting from the noisy environment. Two kinds of TP matrices for the Markovian process are considered: those with polytopic uncertainties and those with partially unknown entries.

21 Introduction 9 Sufficient conditions are established for the existence of the desired filter satisfying the H performance constraint in terms of a set of RLMIs. The other research focus of this chapter is to investigate the fault detection problem for discrete-time MJSs with incomplete knowledge of TPs, RVNs, and sensor saturations. Two energy norm indices are used for the fault detection problem: one to account for the restraint of disturbance and the other to account for sensitivity of faults. The characterization of the gains of the desired fault detection filters is derived in terms of the solution to a convex optimization problem that can be easily solved by using the semi-definite program method. 6. Chapter 6 is concerned with the quantized fault detection problem for two classes of discrete-time nonlinear systems with stochastic mixed time-delays and successive packet dropouts. The mixed time-delays comprise both the multiple discrete time-delays and the infinite distributed delays that occur in a random way. The fault detection problem is first considered for a class of discrete-time systems with randomly occurring nonlinearities, mixed stochastic time-delays, and measurement quantizations. A sequence of stochastic variables is introduced to govern the random occurrences of the nonlinearities, discrete time-delays, and distributed time-delays, where all the stochastic variables are mutually independent but obey the Bernoulli distribution. In addition, by using similar analysis techniques, the network-based robust fault detection problem is also investigated for a class of uncertain discrete-time T S fuzzy systems with stochastic mixed time-delays and successive packet dropouts. 7. Chapter 7 is concerned with the distributed H filtering problem for a class of nonlinear systems with ROSSs and successive packet dropouts over sensor networks. The issue of ROSSs is brought up to account for the random nature of sensor saturations in a networked environment of sensors and, accordingly, a novel sensor model is proposed to describe both the ROSSs and successive packet dropouts within a unified framework. Two sets of Bernoulli-distributed white sequences are introduced to govern the random occurrences of the sensor saturations and successive packet dropouts. Through available output measurements from not only the individual sensor but also its neighboring sensors, a sufficient condition is established for the desired distributed filter to ensure that the filtering dynamics is exponentially mean-square stable and the prescribed H performance constraint is satisfied. The solution of the distributed filter gains is characterized by solving an auxiliary convex optimization problem. 8. Chapter 8 is concerned with the distributed finite-horizon filtering problem for a class of time-varying systems over lossy sensor networks. The time-varying system (target plant) is subject to RVNs caused by environmental circumstances. The lossy sensor network suffers from quantization errors and successive packet dropouts that are described in a unified framework. Two mutually independent sets of Bernoulli-distributed white sequences are introduced to govern the random occurrences of the RVNs and successive packet dropouts. Through available output measurements from both the individual sensor and its neighboring sensors according to the given topology, a sufficient condition is established for the desired distributed finite-horizon filter to ensure that the prescribed average filtering performance constraint is satisfied. The solution of the distributed filter gains is characterized by solving a set of RLMIs. 9. Chapter 9 is concerned with the distributed H filtering problem for a class of discretetime Markovian jump nonlinear time-delay systems with deficient statistics of modes transitions. The system measurements are collected through a lossy sensor network

22 10 Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information subject to randomly occurring quantization errors (ROQEs) and randomly occurring packet dropouts (ROPDs). The system model (dynamical plant) includes the modedependent Lipschitz-like nonlinearities. The description of deficient statistics of modes transitions is comprehensive, accounting for known, unknown, and uncertain TPs. Two sets of Bernoulli-distributed white sequences are introduced to govern the phenomena of ROQEs and ROPDs in the lossy sensor network. We aim to design the distributed H filters through available system measurements from both the individual sensor and its neighboring sensors according to a given topology. The stability analysis is first carried out to obtain sufficient conditions for ensuring stochastic stability, as well as the prescribed average H performance constraint for the dynamics of the estimation errors, and then a filter design scheme is outlined by explicitly characterizing the filter gains in terms of some matrix inequalities. 10. In Chapter 10, a new stochastic H filtering approach is proposed to deal with the localization problem of the mobile robots modeled by a class of discrete nonlinear time-varying systems subject to missing measurements and quantization effects. The missing measurements are modeled via a diagonal matrix consisting of a series of mutually independent random variables satisfying certain probabilistic distributions on the interval [0, 1]. The measured output is quantized by a logarithmic quantizer. Attention is focused on the design of a stochastic H filter such that the H estimation performance is guaranteed over a given finite horizon in the simultaneous presence of plant nonlinearities (in the robot kinematic model and the distance measurements), probabilistic missing measurements, quantization effects, linearization error, and external non-gaussian disturbances. A necessary and sufficient condition is first established for the existence of the desired time-varying filters in virtue of the solvability of certain coupled recursive Riccati difference equations (RDEs). Both theoretical analysis and simulation results are provided to demonstrate the effectiveness of the proposed localization approach. 11. In Chapter 11, we sum up the results of the book and discuss some related topics for future research work.

23 2 Variance-Constrained Finite-Horizon Filtering and Control with Saturations This chapter addresses the robust H finite-horizon filtering and output feedback control problems for a class of uncertain discrete stochastic nonlinear time-varying systems with sensor and actuator saturations, error variance constraints, and multiple missing measurements. In the system under investigation, all the system parameters are allowed to be time varying, and the stochastic nonlinearities are described by statistical means which can cover several classes of well-studied nonlinearities. First, we develop a new robust H filtering technique for the nonlinear discrete time-varying stochastic systems with norm-bounded uncertainties, multiple missing measurements, and error variance constraints. The missing measurement phenomenon occurs in a random way, and the missing probability for each sensor is governed by an individual random variable satisfying a certain probabilistic distribution on the interval [0, 1]. Sufficient conditions are derived for a finite-horizon filter to satisfy both the estimation error variance constraints and the prescribed H performance requirement. Such a technique relies on the forward solution to a set of RLMIs and, therefore, is suitable for online computation. Second, the corresponding robust H finite-horizon output feedback control problem is investigated for such types of stochastic nonlinearities with both sensor and actuator saturations. The parameter uncertainties are assumed to be of the polytopic type. Sufficient conditions are first established for the robust H performance through intensive stochastic analysis, and then an RLMI approach is employed to design the desired output feedback controller achieving the prescribed H disturbance rejection level. Finally, some illustrative examples are exploited to show the effectiveness and applicability of the proposed filter and controller design schemes. Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information, First Edition. Hongli Dong, Zidong Wang, and Huijun Gao John Wiley & Sons, Ltd. Published 2013 by John Wiley & Sons, Ltd.

24 12 Filtering, Control and Fault Detection with Randomly Occurring Incomplete Information 2.1 Problem Formulation for Finite-Horizon Filter Design Consider the following discrete uncertain nonlinear time-varying stochastic system defined on k [0, N]: x k+1 = (A k + A k )x k + f k + D 1k w k y ck = B k x k + g k + D 2k w k, (2.1) z k = C k x k where x k R n represents the state vector, y ck R r is the process output, z k R m is the signal to be estimated, w k R p is a zero-mean Gaussian white-noise sequence with covariance W > 0, and A k, B k, C k, D 1k, and D 2k are known, real, time-varying matrices with appropriate dimensions. The parameter uncertainty A k is a real-valued time-varying matrix of the form A k = H k F k E k, (2.2) where H k and E k are known time-varying matrices with appropriate dimensions, and F k is an unknown time-varying matrix satisfying F k F T k I. The functions f k = f (x k, k) and g k = g(x k, k) are stochastic nonlinear functions which are described by their statistical characteristics as follows: {[ ] } fk E x g k = 0, (2.3) k {[ ] fk [ E f T g j g T ] } j x k = 0, k j, (2.4) k and {[ ] fk [ E f T g k k g T k ] } x k = := := q π i π T i E { x T k Ɣ i x k } [ π1i q ][ ] T π1i E { x π 2i π k T Ɣ } i x k 2i [ ] q θ i 11 θ12 i (θ12 i )T θ22 i E { xk T Ɣ } i x k, (2.5) where π 1i, π 2i, θ i jl, and Ɣ i ( j, l = 1, 2; i = 1, 2,...,q) are known matrices. Remark 2.1 As pointed out by Yaz and coworkers [145, 146], the nonlinearity description in (2.3) (2.5) encompasses many well-studied nonlinearities in stochastic systems such as (1) linear system with state- and control-dependent multiplicative noise; (2) nonlinear systems with random vectors dependent on the norms of states and control input; and (3) nonlinear systems with a random sequence dependent on the sign of a nonlinear function of states and control inputs.